The rotor of the instant invention is used in air motors ranging in size from a fraction of a horsepower to several horsepower and even to many horsepower. The bucket-type rotor distinguishes the pneumatic motor in which it operates from the vane-type air motor. Rotors for the instant type of motor define an annular row of spaced air scoops which rotate at high speed past an air injector nozzle which drives the motor.
Motors of this type are characterized by being high-speed and low-torque, and would ordinarily require some speed reduction from the rotor speed even for relatively high-speed applications such as for ventilation fans. In order to produce even that amount of torque, the rotor would spin at velocities on the order of 10,000 to 25,000 RPM, with a speed reduction from as little as 2:1 to as much as 12:1.
There are several problems with air motors which have prevented their introduction for general use to replace electric motors, and particularly electric motors which operate in explosion-prone areas in which explosion-proof or spark-proof electric motors are required. Air motors would seem a natural for such applications, but due to the perception on the part of industry that they are loud, require frequent maintenance, and are subject to dangerous rotor fragmentation at high speeds, they have not been generally accepted.
This patent application is co-pending with an application on an air motor which is designed specifically to overcome or minimize the problems associated with air motors, resulting in the production of an air motor which is an alternative to electric motors.
The instant invention pertains to the rotor of the motor of the co-pending application, and is particularly addressed to eliminating the danger inherent in the use of such motors resulting from rotor fragmentation that occurs when using air motors with other types of rotors, when there is a runaway rotor condition in which the rotor is operating at speeds much higher than that for which it is designed.
Other rotors have been developed to eliminate this problem, two of which are disclosed in U.S. Pat. Nos. 4,509,896, and 4,507,047. Those inventions pertain to rotors having an expandable outer ring which expands under the action of centrifugal force to bind against the walls of the chamber in which it rotates when it is over-driven causing it to automatically reduce speed, or at least fail to accelerate, beyond a certain speed.
Although this is certainly a legitimate approach to the solution to the rotor fragmentation problem, it is structurally somewhat complicated and results in considerable wear on the rotor mechanism if it is overdriven too often.
There is a need for a rotor which avoids or resolves the over -driving problem, in a simple and inexpensive and fool-proof manner.